The objective of the proposed research is to define the mechanisms involved in controlling the rate of differentiation of precursor cells in the basal layer of trachael-bronchial membrane to serous cells and mucus secreting goblet cells at the surface. The increased synthesis of mucin glycoproteins in this tissue is usually accompanied by a corresponding increase in the number of mucus secreting goblet cells and the rate of formation of these acidic sulfated glycoproteins may be controlled, in part, by the proliferation or increased formation of mucus secreting cells. Goblet cells have been isolated from the surface of porcine trachael membranes by a new procedure utilizing a proteolytic enzyme which does not attack these epithelial cells. The denuded trachea explant can reform a surface layer containing goblet, serous and ciliated cells after a period of incubation in organ culture. The newly formed surface layer can once again secret acidic mucin glycoproteins. The in vitro growth requirements of these isolated cells are being determined. Other cells will be isolated from the denuded trachea membranes used to prepare the surface epithelial cells in order to determine which cell types are precursors of the fully differentiated mucus secreting cells. The trachea organ culture and isolated cell systems will be used to examine the regulation of mucin glycoprotein synthesis under conditions mimicking hypersecretion. The influence of various irritants on the rate of synthesis and composition of the oligosaccharide units of mucin glycoproteins will be examined with these isolated cells and denuded tracheal explant systems. Many diseases of the respiratory tract are accompanied by an increase in the rate of formation of mucus, and in some diseases an abnormal mucus is formed. The study of these processes with isolated cells may provide a pertinent model system with which to examine the reparative process of mucus secreting respiratory epithelium.